1. Field of the Invention
The present invention generally relates to attachment structures of semiconductor device sockets, and, more particularly, to an attachment structure of a semiconductor device socket attached to a test circuit substrate.
In recent years, there has been an increasing demand for lighter and smaller portable terminals and portable equipment such as portable telephones. Therefore, semiconductor devices mounted on such terminals and equipment need to be lighter and smaller accordingly. Also, as semiconductor devices are becoming smaller, the pitch of bumps is becoming extremely small.
When a reliability test is conducted on a semiconductor device, the semiconductor device is mounted on a semiconductor device socket. Therefore, semiconductor device sockets are also required to have very small pitch.
2. Description of the Related Art
FIGS. 1A to 1C show a conventional semiconductor device socket (hereinafter referred to as "socket"). A socket 10A is used for a test, such as a burn-in test for reliability, of a semiconductor device 1 having a BGA (Ball Grid Array) package structure, for instance.
As shown in FIGS. 1A and 1B, the socket 10A comprises a socket body 11, a lid body 12, and contacts 13. The socket body 11 accommodates the contacts 13, and is provided with a seat member 14. The seat member 14 has insertion holes 25 formed in positions corresponding to the positions of bumps 2 as shown in FIG. 1C. The upper ends of the contacts 13 are inserted into the insertion holes 25. The lower ends of the contacts 13 extend outwardly from the bottom surface of the socket body 11, and are soldered to a test circuit substrate (not shown). The seat member 14 is provided with guides 15 for guiding the mounting of the semiconductor device 1.
The lid body 12 is attached to the socket body 11, and can be freely opened and closed. The lid body 12 is closed after the semiconductor device 1 is set in the socket body 11. By closing the lid body 12, a presser portion 16 attached to the lid body 12 presses the semiconductor device 1 against the contacts 13. By doing so, the bumps 2 formed on the semiconductor device 1 can be surely connected to the contacts 13, so that the semiconductor device 1 can be electrically connected to the contacts 13. Reference numeral 17 indicates a latch which is engaged with the socket body 11 when the lid body 12 is closed, so as to prevent the lid body 12 from opening during a test of the semiconductor 1.
The conventional contacts 13 provided to the socket 10A are flat spring-type contacts formed by press molding. However, it is difficult to form very small flat spring-type contacts. As a result, the flat spring-type contacts are becoming less suitable for the semiconductor device 1 having the extremely small bump pitch.
In place of sockets having such flat spring-type contacts, contact film-type sockets have been suggested. FIGS. 2A and 2B show a socket 10B of a conventional contact film type. FIG. 2A shows the entire view of the socket 10B, and FIG. 2B shows the connection structure between contacts 20 and a test circuit substrate 25. In these figures, the socket 10B is a socket for BGA packaging.
A contact film 18 comprises a base film 26 made of polyimide or the like, and extension conductive wires 19 formed on the base film 26. The extension conductive wires 19 have the contacts 20 on their inner side, and a connection portion 27 on their outer side. The contacts 20 are connected to the bumps 2 of the semiconductor device 1, and therefore protrude upward penetrating the base film 26. The connection portion 27 is connected to flat spring contacts 22. Accordingly, the contacts 20 are connected to the connection portion 27 via the extension conductive wires 19. The contact film 18 is first fixed to a package guide 21, and then attached to the socket body 11. The contact film 18 has the same structure as TAB (Tape Automated Bonding) tape having a wiring pattern formed on a resin film. With this contact film 18, the extension conductive wires 19 and the contacts 20 can be made very small. Accordingly, the socket 10B can be used for the semiconductor device 1 having very small bump pitch.
With the socket 10B shown in FIGS. 2A and 2B, however, the connection structure between the contact film 18 and the test circuit substrate 25 is a problem. Generally, the flat spring contacts 22 are disposed in the socket body 11, and the contact film 18 and the test circuit substrate 25 are connected by the flat spring contacts 22. In this connection structure, the upper ends of the flat spring contacts 22 are connected to the connection portion 27 of the extension conductive wires 19, and the lower ends of the flat spring contacts 22 are soldered to the test circuit substrate 25. Thus, the contact film 18 and the test circuit substrate 25 are connected via the flat spring contacts 22.
When connecting the socket 10B to the test circuit substrate 25, it is necessary to make the flat spring contacts 22 elastic. Accordingly, the flat spring contacts 22 become long, and the wiring distance from the contacts 20 to the test circuit substrate 25 also becomes long. As a result, the electric characteristics, especially high-frequency characteristics, deteriorate due to the long wiring distance.
When the lid body 12 is closed with the semiconductor device 1 inside, the presser portion 16 presses the contacts 20 via the semiconductor device 1, a package guide presser portion 23 presses the package guide 21, and the flat spring contacts 22 press the connection portion 27. As a result, a very heavy load is applied to the socket 10B, which needs to have great strength.
For this reason, the conventional socket 10B has the socket body 11 and the lid body 12 that are thick enough to endure the heavy load. With such a structure, the socket 10B becomes larger in size, and the number of sockets 10B that can be mounted on one test circuit substrate 25 (a burn-in board, for instance) becomes smaller accordingly. Also, as one socket 10B becomes larger in size, it becomes more expensive.
FIGS. 3A and 3B show a socket 10C of another contact film type. This socket 10C has spring probes 24, instead of the flat spring contacts 22, for connecting the contact film 18 and the test circuit substrate 25. Each of the spring probes 24 has a spring inside, and the top end thereof is elastically pushed outward. Compared with the flat spring contacts 22, the spring probes 24 can be made small enough to be compatible with the minutely patterned contact film 18. However, because of the minuteness, the spring probes 24 are expensive, and result in high production costs when combined with the minutely patterned film contact 18.
Another problem with the socket 10C is that since the built-in spring pushes the contact portion 27, the load applied to the socket 10C is heavy. To endure such a heavy load, the socket 10C needs to be made large in size.